Congruent power and timing signals for device

ABSTRACT

Congruent power and timing signals in a single electronic device. In an embodiment, a circuit may include just one isolation transformer operable to generate a power signal and a timing signal. On the secondary side, two branches may extract both a power signal and a clock signal for use in the circuit on the isolated secondary side. The first branch may be coupled to the transformer and operable to manipulate the signal into a power signal, such as a 5V DC signal. Likewise, the second circuit branch is operable to manipulate the signal into a clock signal, such as a 5 V signal with a frequency of 1 MHz. By extracting both a power supply signal and a clock signal from the same isolation transformer on the secondary side, valuable space may be saved on an integrated circuit device with only having a single winding for a single isolation transformer.

BACKGROUND

Systems and devices often rely upon two kinds of signals for operation.A power signal may be used to provide power, logic, and control signalswithin a system or device. Further, a timing signal or clock signal mayalso be used to trigger, manipulate or otherwise control variouscomponents and circuits of a system or device. Thus, together, these twokinds of signals may be used accordingly.

Often times, a system or device may have the above-described signalsprovided externally from the system or device. That is, the power signaland/or the clock signal may originate from a circuit outside the systemor device. For example, when monitoring overhead power lines, a devicefor monitoring may draw power directly from the power lines themselves.Similarly, in a device having multiple integrated circuit (IC) chips ormultiple separate printed circuit boards (PCB), a single clock sourcemay provide timing signals for all components in a device. Furthermore,these signals, when originating outside of ICs, PCBs, or specificseparate devices, may require isolation before being used within thesecomponents. As such, both the power signals and the timing signals mayrequire isolating transformers for each kind of signal to provide theisolated signals for use on-chip. Providing two isolating transformersfor these two sets of signals is cumbersome and inefficient.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the subject matter disclosed herein will become morereadily appreciated as the same become better understood by reference tothe following detailed description, when taken in conjunction with theaccompanying drawings.

FIG. 1 is a block diagram of a conventional system for providing a powersignal and a timing signal to a device using two different isolationtransformers.

FIG. 2 is a block diagram of a system for providing a power signal and atiming signal to a device using one isolation transformer according toan embodiment of the subject matter disclosed herein.

FIG. 3 is a block diagram of a system for providing a power signal and atiming signal to devices of a three-phase power system using oneisolation transformer per device according to an embodiment of thesubject matter disclosed herein.

DETAILED DESCRIPTION

The following discussion is presented to enable a person skilled in theart to make and use the subject matter disclosed herein. The generalprinciples described herein may be applied to embodiments andapplications other than those detailed above without departing from thespirit and scope of the present detailed description. The presentdisclosure is not intended to be limited to the embodiments shown, butis to be accorded the widest scope consistent with the principles andfeatures disclosed or suggested herein.

Prior to discussing the specific details of various embodiments, anoverview of one embodiment of the subject matter is presented.Electronic circuits may often use two different kinds of signals asdiscussed above—power signals and clock signals. According to variousembodiment discussed below, a single signal may be used to provide botha power signal and a clock signal to a circuit via a single isolationtransformer. In one embodiment, an integrated circuit may include justone isolation transformer operable to generate an isolated signal on itssecondary side that is proportional to an initial signal received from asignal source. On the secondary side, two branches may then extract botha power signal and a clock signal for use in the circuit on the isolatedsecondary side. The first branch may be coupled to the transformer andoperable to manipulate the signal into a power signal, such as a 5V DCsignal. Likewise, the second circuit branch is operable to manipulatethe signal into a clock signal, such as a 5 V signal with a frequency of1 MHz. By extracting both a power supply signal and a clock signal fromthe same isolation transformer on the secondary side, valuable space maybe saved on an integrated circuit device with only having a singlewinding for a single isolation transformer. These and other aspects ofthe embodiments are discussed below in greater detail.

FIG. 1 is a block diagram of a conventional system for providing a powersignal and a timing signal to a device using two different isolationtransformers. In this system 100, a clock source 110 (which may beexternal to the IC, PCB, or device 105) may provide an initial clocksignal to the primary side of a first isolation transformer 111. Theisolation transformer then translates the signal into a secondary-sidesignal that be used to provide a clock signal CLK to an IC 105(hereinafter, reference to an IC 105 is understood to mean an IC, PCB,or other component/device). The secondary side of the first isolationtransformer 111 is also coupled to a ground GND.

Similarly, yet separately, a power source 120 (again, possibly external)may provide a power signal to the primary side of a second isolationtransformer 121. The second isolation transformer then translates apower signal on its secondary side to provide such the power signal Vccto the IC 105. As before, the secondary side of the second isolationtransformer 121 may also be coupled to the ground GND.

In this manner, both a power signal Vcc and a clock signal CLK aregenerated external to the IC 105, yet provided to the IC in an isolatedmanner through the two different isolation transformers 110 and 120.However, with two different isolation transformers 110 and 120, morespace is required for the two different transformer windings. Space maybe at a premium in smaller and more efficient devices and therequirement for two different sets of transformer windings is adisadvantage. As is described with respect to FIG. 2, however, if theclock signal can be “piggy-backed” onto the power signal, then only asingle isolation transformer may be needed.

FIG. 2 is a block diagram of a circuit 200 for providing a power signaland a timing signal to a device using one isolation transformeraccording to an embodiment of the subject matter disclosed herein. Inthis embodiment a power/clock source 225 may provide a signal having aspecific frequency and amplitude. A suitable frequency may be 1 MHz anda suitable voltage magnitude may be 12 V. Since common power sources maybe different (e.g., a North American Standard of 120 V and 60 Hz), sucha 12 V, 1 MHz signal may be derived according to conventional solutionsfor changing the frequency and voltage amplitude of a signal. In thisexample and the following example below with respect to FIG. 3, theoriginal signal may be a common power line source having an initialfrequency of 60 Hz and 240 V. Such conventional manners of manipulatinga voltage signal are not discussed in greater detail herein.

The power/clock source 225 provides a signal to the primary side of asingle isolation transformer 230. The isolation transformer 230 thengenerates an almost identical signal at its secondary winding since theisolation transformer has an equivalent number of windings on each side.The initial 12V, 1 MHz signal passes through a filter capacitor 250 tofilter out any low-end transients. After this initial filtering, theoscillating (and now filtered) signal may be manipulated in one two waysto deliver either a clock signal to the component 205 or a power signalto the component 205.

In the case of the power signal manipulation, the circuit includes zenerdiode 253 connected between the output of the filter capacitor andground GND. The zener diode 253 is sized so as to clamp the magnitude ofthe voltage of the signal at node 260 to 5 V. The circuit then furtherincludes a rectifying diode 252 that rectifies the clamped signal toprovide a DC supply voltage to the Vcc node of the component 205. ThisDC supply voltage is filtered a second time by filter capacitor 254 toremove any high-frequency transients. Thus, a filtered, rectified, andclamped 5V power signal is delivered to Vcc.

In the case of the clock signal manipulation, the zener diode 253, asdescribed above, clamps the signal at node 260 to 5 V. Node 260 iscoupled to the clock input CLK of the component 205 through an impedance251. This impedance 251 may be sized to further reduce the voltage ofthe clock signal as it enters the clock node. Further, without anyrectification, the frequency of the clock signal will be the same as thefrequency of the initial power/clock signal from the secondary windingof the isolation transformer 230.

Such a solution is advantageous because both the clock signal CLK andthe power signal Vcc may be derived from a single signal that passesthrough a single isolation transformer 230. Having only a singleisolation transformer 230 reduces the space needed in a device or on anIC or PCB because of the reduced number of windings in the singletransformer. When IC space is at a premium, such a reduction in windingspace provides a distinct advantage. Thus, the circuit 200 may be partof a larger system as discussed below with respect to FIG. 3.

FIG. 3 is a block diagram of a system 300 for providing a power signaland a clock signal to measurement devices of a three-phase power systemusing one isolation transformer per device according to an embodiment ofthe subject matter disclosed herein. Such a system 300 may be usedwithin the context of a three-phase power distribution system. Forexample, the system 300 may include a set of power lines having fourconductors, phase A 310 a, phase B 310 b, phase C 310 c and a neutralconductor 311. Often times, it may be useful to know the voltage andcurrent characteristics at any point in time for each of theseconductors. Thus, each conductor may be coupled to both a dedicatedcurrent sensor 320 a-c and a dedicated voltage sensor 321 a-c.

In the system of FIG. 3 then, phase A 310 a may be coupled to a firstvoltage sensor 321 a and a first current sensor 320 a. Similarly, phaseB 310 b may be coupled to a second voltage sensor 321 b and a secondcurrent sensor 320 b just as phase C 310 c may be coupled to a thirdvoltage sensor 321 c and a third current sensor 320 c. A skilled artisanunderstands that each of these sensors may include circuitry forgenerating signals proportional to the voltages and currents on theconductors as handling such large voltages and currents directly may bedangerous. As such, these values are transformed to signals bettersuited for use in the circuits 302 a-c.

In this system 300 embodiment, several devices and/or components may bepowered from a single source that may or may not be part of the samecircuit and/or IC in the system. Here, there are four different circuitsshown in the system 300 of FIG. 3. A first circuit 340 may be used toprovide a common power/clock signal to each of the other three circuits302 a-c. Each of these three circuits 302 a-c may comprise the circuit200 shown in FIG. 2. In this manner, each circuit 302 a-c may beprovided a single power/clock signal such that each circuit onlyincludes one isolation transformer. Further, each of these circuits 302a-c may be coupled to respective currents sensors 320 a-c and respectivevoltage sensors 321 a-c to receive measurement signals from the actualconductors 310 a-c of the three-phase power system.

The first circuit 340 may be coupled to a voltage source for initiallygenerating a power signal. In one embodiment, this power source may beone of the power lines; as shown, the circuit 340 is coupled to thevoltage sensor 321 c for Phase C 310 c. In other embodiments, thisinitial power source may be a battery or other suitable power source.The circuit 340 may then manipulate the initial power signal to providea suitable power/clock signal to the other three circuits 302 a-c.Further, the first circuit may include a processor 390 operable toperform calculations based upon data received back from other circuitsin the system. Further yet, calculated data may be stored in a memory391.

Thus, the power/clock signal is initially provided as a clock signalwith a frequency of 1 MHz which will have a relatively low magnitude.This signal is conditioned by impedance 331. So, instead providing thisclock signal directly to the three circuits 302 a-c, the clock signal isused to drive a switching transistor 330 that switches a 12-volt supplyvoltage through the primary side of each isolation transformer for eachrespective circuit 302 a-c. Further, a filter capacitor 332 filters outlow-frequency transients. In this manner, each circuit is provided witha power/clock signal having a voltage of 12 V and a frequency of 1 MHz.

Such a circuit 340 for generating the power/clock signal may be otherconfigurations. Any circuit that can generate an oscillating signal witha specific voltage magnitude and frequency may be used to generate thepower/clock signal. Furthermore, any type of filtering arrangement onthe secondary side of each isolation transformer may be used to drivethe IC supply voltages. Further yet, any type of separate filteringcould be used to recover the clock signal for use at the IC as well.

On particular alternative technique generating a power/clock signal maybe a circuit having a feedback signal from the secondary side of eachcircuit 302 a-c. Such a feedback signal would be sent back through therespective isolation transformer, but could then be used to modulate theduty cycle of the initial clock signal. By maintaining the frequency ofthe initial clock signal (e.g., leading edges of pulses still occur at a1 MHz frequency), one could modulate the duty cycle to modulate thepower delivered (e.g., the length of each pulse could vary).

Within the context of the system of FIG. 3, one could use the threecircuits 302 a-c for measuring the current and voltage characteristicsof each phase 310 a-c. Each of these circuits 302 a-c may include an IC(such as 205 from FIG. 2) that may be include Sigma Delta modulatorsthat may be used to sense current and voltage on a particular phase of apower supply. So for example, in the case of a three-phase power supply,one could use information garnered from these circuits 302 a-c tocalculate the entire power usage based on the readings from each phase.Additional information could be garnered from the neutral conductor 311as well if one were couple a sensor (not shown) here as well.

Each of the circuits 340 and 302 a-c as well as the sensors 320 a-c and321 a-c may be housed within a single device such as a power meter.Alternatively, the sensors 320 a-c and 321 a-c may be housed in separatededicated devices that may be located near the conductors 310 a-c, suchthat only small measurement signals are sent to a separate devicehousing the additional circuits of the system 300. Further yet, allcircuits described in the system of FIG. 3 may be resident on a singleIC.

While the subject matter discussed herein is susceptible to variousmodifications and alternative constructions, certain illustratedembodiments thereof are shown in the drawings and have been describedabove in detail. It should be understood, however, that there is nointention to limit the claims to the specific forms disclosed, but onthe contrary, the intention is to cover all modifications, alternativeconstructions, and equivalents falling within the spirit and scope ofthe claims.

What is claimed is:
 1. A metering method comprising: operating aplurality of measurement circuits each coupled to an associated phasevoltage sensor and a phase current sensor of a respective phase of amultiphase power system, each measurement circuit comprising atransformer generating an isolated signal, a first circuit branchcoupled to the transformer and manipulating the isolated signal into aclamped power signal, and a second circuit branch coupled to thetransformer and manipulating the isolated signal into a clock signal. 2.The method of claim 1, wherein the transformer comprises an isolationtransformer having a primary winding and a secondary winding havingapproximately equal length.
 3. The method of claim 1, wherein the firstcircuit branch comprises: a zener diode coupled to the transformer andclamping the voltage of the isolated signal to a limit voltage; arectifying diode coupled to the transformer and rectifying the isolatedsignal; and a filter capacitor coupled to the rectifying diode andremoving high-frequency transients from the isolated signal.
 4. Themethod of claim 3, wherein the limit voltage is 5 volts.
 5. The methodof claim 3, further comprising a low-pass filter coupled to therectifying diode and attenuating high-frequency transients.
 6. Themethod of claim 1, wherein the second circuit branch comprises animpedance reducing the voltage of the isolated signal to a clock signalvoltage.
 7. The method of claim 1, wherein the isolated signal comprisesa signal having a frequency of 1 MHz and a voltage of 12 volts.
 8. Themethod of claim 1, wherein the measurement circuit comprises a high-passfilter coupled to the transformer and attenuating low-frequencytransients.
 9. A method comprising: receiving an initial signal at aprimary side of a transformer; clamping, using a first diode, a voltagesignal at a secondary side of the transformer to a limit voltage at acathode of the first diode and at an anode of a second diode, whereinthe cathode of the first diode is coupled to form a node with an anodeof the second diode; rectifying, using the second diode, the clampedvoltage signal to produce a rectified and clamped voltage signal at acathode of the second diode; filtering the rectified and clamped voltagesignal to remove high-frequency transients to produce a power signalthat is proportional to the initial signal; and extracting a clocksignal at the secondary side of the transformer that is proportional tothe initial signal.
 10. The method of claim 9, further comprising:supplying the power signal to a device; and supplying the clock signalto the device.
 11. The method of claim 9, further comprising isolatingthe initial signal from the power signal and isolated from the extractedclock signal.
 12. The method of claim 9, wherein extracting the powersignal further comprises filtering the power signal to removelow-frequency transients.
 13. A method comprising: receiving an initialsignal at a primary side of a transformer coupled to a phase sensor fora multi-phase line; clamping, using a zener diode, a voltage signal at asecondary side of the transformer to a limit voltage at a cathode of thezener diode and at an anode of a diode, wherein the cathode of the zenerdiode is coupled to form a node with an anode of the diode; rectifying,using the diode, the clamped voltage signal to produce a rectified andclamped voltage signal at a cathode of the diode; filtering therectified and clamped voltage signal to remove high-frequency transientsto produce a power signal that is proportional to the initial signal;and extracting a clock signal at the secondary side of the transformerthat is related to the initial signal.
 14. The method of claim 13,wherein the phase sensor comprises one of a voltage phase sensor and acurrent phase sensor.
 15. The method of claim 13, further comprising:supplying the power signal to a device; and supplying the clock signalto the device.
 16. The method of claim 13, further comprising isolatingthe initial signal from the power signal and isolated from the extractedclock signal.
 17. The method of claim 13, wherein extracting the powersignal further comprises filtering the power signal to removelow-frequency transients.